In Patent Literatures 1 and 2, a same frequency (CO-CH: CO-Channel) radio communication system that performs radio communication utilizing vertical polarization and horizontal polarization at the same frequency is described. In the radio communication system, two lines corresponding to the vertical polarization and the horizontal polarization can be utilized for communication. Therefore, usage of the two lines improves the throughput in comparison with a case where only the vertical polarization or horizontal polarization is used for a single transmission.
However, in the CO-CH transmission system, mutual interference occurs between the vertical polarization and the horizontal polarization, so that there is a possibility of communication quality in the CO-CH transmission system being reduced due to mutual interference between the polarizations. In addition, in the CO-CH transmission system, the horizontal polarization and the vertical polarization are attenuated due to factors such as bad weather, and as a result, there is a possibility of the communication quality being reduced.
FIG. 1 illustrates an example of a configuration of a typical CO-CH transmission system.
In such a CO-CH transmission system, when an antenna including a high cross polarization discrimination (XPD) is used, and as illustrated in FIG. 1, when cross polarization interference cancellers (XPICs) 2041 and 2051 are provided at the reception side of the CO-CH transmission system, reduction of communication quality due to mutual interference between the polarization can be prevented.